Synthesis of esuberaprost prodrugs

ABSTRACT

Provided are novel prodrugs of esuberaprost and pharmaceutical compositions thereof, as well as methods of making and methods of using these prodrugs.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/748,759, filed Oct. 22, 2018, which application is incorporatedherein by reference in its entirety.

FIELD

The present application relates to prostacyclins and more particularly,to prodrugs of esuberaprost, pharmaceutical compositions thereof, and tomethods of making and using such prodrugs and pharmaceuticalcompositions.

BACKGROUND

Prostacyclin derivatives are useful pharmaceutical compounds possessingactivities such as platelet aggregation inhibition, gastric secretionreduction, lesion inhibition, and bronchodilation Beraprost is asynthetic benzoprostacyclin analogue of natural prostacyclin that iscurrently under clinical trials for the treatment of pulmonaryhypertension and vascular disease (excluding renal disease) in NorthAmerica and Europe. Esuberaprost is a reformulated single isomer ofberaprost currently being developed for the treatment of pulmonaryarterial hypertension and vascular disease.

Beraprost and related benzoprostacyclin analogues are disclosed in U.S.Pat. No. 5,202,447 and Tetrahedron Lett. 31, 4493 (1990). Furthermore,as described in U.S. Pat. No. 7,345,181, several synthetic methods areknown to produce benzoprostacyclin analogues, including thepharmacologically active isomer of beraprost, such as beraprost 314-d(esuberaprost).

Derivatives and prodrugs of existing drugs have the ability to improvethe physicochemical properties of such drugs. Therefore, it is desiredto prepare improved esuberaprost compounds, such as prodrugs, anddevelop efficient, commercially applicable synthetic methods to theprodrugs of esuberaprost.

SUMMARY

An object of the present invention is to provide prodrugs ofesuberaprost, pharmaceutical compositions thereof, process forselectively producing prodrugs of esuberaprost, and methods of usingprodrugs of esuberaprost and pharmaceutical compositions thereof totreat various diseases or disorders.

At least one embodiment may be a compound the Formula (I), or adiastereomer, enantiomer or pharmaceutically acceptable salt of thecompound:

-   -   wherein    -   R¹ and R² each independently represent H, C₁-C₆ alkyl, —CO₂R⁶,        —CONR⁶R⁷, —P(O)(OH)₂—, —(CH₂)₂OP(O)(OH)₂— or a hydroxy        protecting group, or wherein OR¹ or OR² forms an ester of an        amino acid, or wherein R¹ and R² connected to carbonyl to make a        cyclic carbonate group, or wherein OR¹ or OR² together form a        phosphate group;    -   R³ represents NR⁷R⁸, OR⁹, or NHSO₂R¹⁰;    -   R⁴ represents H or C₁₋₃ alkyl;    -   R⁵, R⁶ and R⁷ each independently represent H or C₁₋₆ alkyl, or        wherein R⁶ and R⁷ together with the nitrogen to which they are        attached form a piperidine or a bipiperidine ring;    -   R⁸ represents H, optionally substituted C₁-C₆ alkyl, or

-   -   or wherein R⁷ and R⁸ are such that NR⁷R⁸ is an amide of an amino        acid;    -   R⁹ represents H or C₁-C₆ alkyl, which may be optionally        substituted with a terminal hydroxyl or carboxy group; and    -   R¹⁰ represents H, optionally substituted C₁-C₆ alkyl, optionally        substituted C₆-C₁₀ aryl, optionally substituted C₃-C₈ heteroaryl        or optionally substituted heterocyclyl; with a proviso that all        of R′, R² and R⁸ are not H.

Yet another embodiment is a compound or a pharmaceutically acceptablesalt thereof, wherein the compound having one of the following formulas:

At least one embodiment may be a process for preparation of prodrugs ofesuberaprost. In at least one embodiment, provided are processes for thepreparation of each of a compound of Formula (III), Formula (VI),Formula (VIII), Formula (XI) and Formula (XIV).

Another embodiment may be a pharmaceutical composition, such as an oralpharmaceutical composition, comprising a pharmaceutically effectiveamount of the compound of Formula I and a pharmaceutically acceptableexcipient therefor. Yet other embodiments may be a pharmaceuticalcomposition, such as an oral pharmaceutical composition, comprising thecompound selected from a compound of Formula (III), Formula (VI),Formula (VIII), Formula (XI) or Formula (XIV).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows ¹H NMR spectrum of compound (3).

FIG. 2 shows ¹H NMR spectrum of compound (5).

FIG. 3 shows ¹H NMR spectrum of compound (6).

FIG. 4 shows ¹H NMR spectrum of compound (7).

FIG. 5 shows ¹H NMR spectrum of compound (8).

FIG. 6 shows ¹H NMR spectrum of compound (10).

FIG. 7 shows ¹H NMR spectrum of compound (11).

FIG. 8 shows ¹H NMR spectrum of compound (12).

FIG. 9 shows ¹H NMR spectrum of compound (13).

FIG. 10 shows ¹H NMR spectrum of compound (14).

FIG. 11 shows mass spectrum of compound (3).

FIG. 12 shows mass spectrum of compound (6).

FIG. 13 shows mass spectrum of compound (8).

FIG. 14 shows mass spectrum of compound (11).

FIG. 15 shows mass spectrum of compound (14).

DETAILED DESCRIPTION

As used herein, “about” will be understood by persons of ordinary skillin the art and will vary to some extent depending upon the context inwhich it is used. If there are uses of the term which are not clear topersons of ordinary skill in the art, given the context in which it isused, such as before a numerical designation, e.g., temperature, time,amount, and concentration, including range, indicates approximationswhich may vary by (+) or (−) 10%, 5% or 1%.

The use of the terms “a” and “an” and “the” and similar references inthe context of describing the elements (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. Recitation of ranges of values herein are merely intended toserve as a shorthand method of referring individually to each separatevalue falling within the range, unless otherwise indicated herein, andeach separate value is incorporated into the specification as if it wereindividually recited herein. All methods described herein may beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein, isintended merely to better illuminate the embodiments and does not pose alimitation on the scope of the claims unless otherwise stated. Nolanguage in the specification should be construed as indicating anynon-claimed element as essential.

The expression “comprising” means “including, but not limited to.” Thus,other non-mentioned substances, additives, carriers, or steps may bepresent.

In general, “substituted” refers to an alkyl, alkenyl, alkynyl, aryl,heteroaryl, heterocyclyl, or ether group, as defined below (e.g., analkyl group) in which one or more bonds to a hydrogen atom containedtherein are replaced by a bond to non-H or non-carbon atoms. Substitutedgroups also include groups in which one or more bonds to a carbon(s) orhydrogen(s) atom are replaced by one or more bonds, including double ortriple bonds, to a heteroatom. Thus, a substituted group will besubstituted with one or more substituents, unless otherwise specified.In some embodiments, a substituted group is substituted with 1, 2, 3, 4,5, or 6 substituents. Examples of substituent groups include: halogens(i.e., F, Cl, Br, and I); hydroxyls; alkoxy, alkenoxy, alkynoxy,aryloxy, aralkyloxy, heterocyclyloxy, and heterocyclylalkoxy groups;carbonyls (oxo); carboxyls; esters; urethanes; oximes; hydroxylamines;alkoxyamines; aralkoxyamines; thiols; sulfides; sulfoxides; sulfones;sulfonyls; sulfonamides; amines; N-oxides; hydrazines; hydrazides;hydrazones; azides; amides; ureas; amidines; guanidines; enamines;imides; isocyanates; isothiocyanates; cyanates; thiocyanates; imines;nitro groups; nitriles (i.e., CN); and the like.

As used herein, “alkyl” groups include straight chain and branched alkylgroups having from 1 to about 20 carbon atoms, and typically from 1 to12 carbons or, in some embodiments, from 1 to 8 carbon atoms. Asemployed herein, “alkyl groups” include cycloalkyl groups as definedbelow. Alkyl groups may be substituted or unsubstituted. Examples ofstraight chain alkyl groups include methyl, ethyl, n-propyl, n-butyl,n-pentyl, n-hexyl, n-heptyl, and n-octyl groups. Examples of branchedalkyl groups include, but are not limited to, isopropyl, sec-butyl,t-butyl, neopentyl, and isopentyl groups. Representative substitutedalkyl groups may be substituted one or more times with, for example,amino, thio, hydroxy, cyano, alkoxy, and/or halo groups such as F, Cl,Br, and I groups. As used herein the term haloalkyl is an alkyl grouphaving one or more halo groups. In some embodiments, haloalkyl refers toa per-haloalkyl group.

As used herein, cycloalkyl groups are cyclic alkyl groups such as, butnot limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,cycloheptyl, and cyclooctyl groups. In some embodiments, the cycloalkylgroup has 3 to 8 ring members, whereas in other embodiments the numberof ring carbon atoms range from 3 to 5, 6, or 7. Cycloalkyl groups maybe substituted or unsubstituted. Cycloalkyl groups further includepolycyclic cycloalkyl groups such as, but not limited to, norbornyl,adamantyl, bornyl, camphenyl, isocamphenyl, and carenyl groups, andfused rings such as, but not limited to, decalinyl, and the like.Cycloalkyl groups also include rings that are substituted with straightor branched chain alkyl groups as defined above. Representativesubstituted cycloalkyl groups may be mono-substituted or substitutedmore than once, such as, but not limited to: 2,2-; 2,3-; 2,4-; 2,5-; or2,6-disubstituted cyclohexyl groups or mono-, di-, or tri-substitutednorbornyl or cycloheptyl groups, which may be substituted with, forexample, alkyl, alkoxy, amino, thio, hydroxy, cyano, and/or halo groups.

As used herein, alkenyl groups are straight chain, branched or cyclicalkyl groups having 2 to about 20 carbon atoms, and further including atleast one double bond. In some embodiments alkenyl groups have from 1 to12 carbons, or, typically, from 1 to 8 carbon atoms. Alkenyl groups maybe substituted or unsubstituted. Alkenyl groups include, for instance,vinyl, propenyl, 2-butenyl, 3-butenyl, isobutenyl, cyclohexenyl,cyclopentenyl, cyclohexadienyl, butadienyl, pentadienyl, and hexadienylgroups among others. Alkenyl groups may be substituted similarly toalkyl groups. Divalent alkenyl groups, i.e., alkenyl groups with twopoints of attachment, include, but are not limited to, CH—CH═CH₂, C═CH₂,or C═CHCH₃.

As used herein, “aryl” or “aromatic,” groups are cyclic aromatichydrocarbons that do not contain heteroatoms. Aryl groups includemonocyclic, bicyclic and polycyclic ring systems. Thus, aryl groupsinclude, but are not limited to, phenyl, azulenyl, heptalenyl,biphenylenyl, indacenyl, fluorenyl, phenanthrenyl, triphenylenyl,pyrenyl, naphthacenyl, chrysenyl, biphenyl, anthracenyl, indenyl,indanyl, pentalenyl, and naphthyl groups. In some embodiments, arylgroups contain 6-14 carbons, and in others from 6 to 12 or even 6-10carbon atoms in the ring portions of the groups. The phrase “arylgroups” includes groups containing fused rings, such as fusedaromatic-aliphatic ring systems (e.g., indanyl, tetrahydronaphthyl, andthe like). Aryl groups may be substituted or unsubstituted.

As used herein, heteroalkyl group include straight and branched chainalkyl groups as defined above and further include 1, 2, 3, 4, 5, or 6heteroatoms independently selected from oxygen, sulfur, and nitrogen.Thus, heteroalkyl groups include 1 to 12 carbon atoms, 1 to 10 carbonsor, in some embodiments, from 1 to 8, or 1, 2, 3, 4, 5, or 6 carbonatoms, or any range therein (e.g., 1-4). Examples of heteroalkyl groupsinclude, but are not limited to, —(CH₂CH₂O)₁₋₅CH₃, —(CH₂)₁₋₆O(CH₂)₁₋₆CH₃, —(CH₂)₁₋₆NR_(a)(CH₂)₁₋₆ CH₃, —(CH₂)₁₋₆S(CH₂)₁₋₆ CH₃,—(CH₂)₁₋₆O(CH₂)₁₋₆O(CH₂)₁₋₆ CH₃, —(CH₂)₁₋₆ NR_(a)(CH₂)₁₋₆NR_(a)(CH₂)₁₋₆CH₃, —(CH₂)₁₋₆O(CH₂)₁₋₆O(CH₂)₁₋₆O(CH₂)₁₋₆CH₃,—(CH₂)₁₋₆NR_(a)(CH₂)₁₋₆NR_(a)(CH₂)₁₋₆NR_(a)(CH₂)₁₋₆CH₃, with the totalnumber of carbon atoms in the heteroalkyl group being 1 to 12 and Ra isa H or a substituted or unsubstituted alkyl, alkenyl, aryl or aralkylgroup. Other examples of heteroalkyl groups include, but are not limitedto, groups having different heteroatoms in a single group. Such examplesof heteroalkyl groups include, but are not limited to, —(CH₂)₁₋₆S(CH₂)₁₋₆O(CH₂)₁₋₆, —(CH₂)₁₋₆ NR_(a)(CH₂)₁₋₆)O(CH₂)₁₋₆,—(CH₂)₁₋₆O(CH₂)₁₋₆ NR_(a)(CH₂)₁₋₆S(CH₂)₁₋₆,—(CH₂)₁₋₆NR_(a)(CH₂)₁₋₆O(CH₂)₁₋₆S(CH₂)₁₋₆, with the total number ofcarbon atoms in the heteroalkyl group being 1 to 12. In someembodiments, heteroalkyl groups include, but are not limited to,polyoxyethylene groups, such as —(OCH₂CH₂—)₁₋₅CH₃, for example,—O(CH₂)₂O(CH₂)₂₀CH₃, —O(CH₂)₂O(CH₂)₂O(CH₂)₂₀CH₃,—O(CH₂)₂O(CH₂)₂O(CH₂)₂O(CH₂)₂₀CH₃.

As used herein, heterocyclyl groups are non-aromatic ring compoundscontaining 3 or more ring members, of which one or more is a heteroatomsuch as, but not limited to, N, O, and S. In some embodiments, theheterocyclyl group contains 1, 2, 3 or 4 heteroatoms. In someembodiments, heterocyclyl groups include mono-, bi- and tricyclic ringshaving 3 to 16 ring members, whereas other such groups have 3 to 6, 3 to10, 3 to 12, or 3 to 14 ring members. Heterocyclyl groups encompasspartially unsaturated and saturated ring systems, such as, for example,imidazolinyl and imidazolidinyl groups. The phrase also includes bridgedpolycyclic ring systems containing a heteroatom such as, but not limitedto, quinuclidyl. The phrase also includes heterocyclyl groups that haveother groups, such as alkyl, oxo or halo groups, bonded to one of thering members, referred to as “substituted heterocyclyl groups”.Heterocyclyl groups include, but are not limited to, aziridinyl,azetidinyl, pyrrolidinyl, imidazolidinyl, pyrazolidinyl, thiazolidinyl,tetrahydrothiophenyl, tetrahydrofuranyl, dioxolyl, pyrrolinyl,piperidyl, piperazinyl, morpholinyl, thiomorpholinyl, tetrahydropyranyl,and tetrahydrothiopyranyl groups. Representative substitutedheterocyclyl groups may be mono-substituted or substituted more thanonce, such as, but not limited to, morpholinyl groups, which are 2-, 3-,4-, 5-, or 6-substituted, or disubstituted with various substituentssuch as those listed above. The heteroatom(s) may also be in oxidizedform, if chemically possible.

As used herein, heteroaryl groups are aromatic ring compounds containing5 or more ring members, of which, one or more is a heteroatom such as,but not limited to, N, O, and S. Heteroaryl groups include, but are notlimited to, groups such as pyrrolyl, pyrazolyl, triazolyl, tetrazolyl,oxazolyl, isoxazolyl, thiazolyl, pyridinyl, pyridazinyl, pyrimidinyl,pyrazinyl, thiophenyl, benzothiophenyl, furanyl, imidazolyl,benzofuranyl, indolyl, azaindolyl (pyrrolopyridinyl), indazolyl,benzimidazolyl, imidazopyridinyl (azabenzimidazolyl), pyrazolopyridinyl,triazolopyridinyl, benzotriazolyl, benzoxazolyl, benzothiazolyl,benzothiadiazolyl, imidazopyridinyl, isoxazolopyridinyl, thianaphthyl,purinyl, xanthinyl, adeninyl, guaninyl, quinolinyl, isoquinolinyl,tetrahydroquinolinyl, quinoxalinyl, and quinazolinyl groups. Heteroarylgroups include fused ring compounds in which all rings are aromatic suchas indolyl groups and include fused ring compounds in which only one ofthe rings is aromatic, such as 2,3-dihydro indolyl groups. The phrase“heteroaryl groups” includes fused ring compounds and also includesheteroaryl groups that have other groups bonded to one of the ringmembers, such as alkyl groups, referred to as “substituted heteroarylgroups.” Representative substituted heteroaryl groups may be substitutedone or more times with various substituents such as those listed above.The heteroatom(s) may also be in oxidized form, if chemically possible.

As used herein, the term “halogen” or “halo” as used herein refers tobromine, chlorine, fluorine, or iodine. In some embodiments, the halogenis fluorine. In other embodiments, the halogen is chlorine or bromine.The term “halide” as used herein refers to the anion of a halogen, suchas bromide, chloride, fluoride, and iodide. In some embodiments, thehalide is chloride or iodide.

As used herein, the terms “alkoxy” refers to a substituted orunsubstituted alkyl group bonded to an oxygen atom. Examples include butare not limited to methoxy and ethoxy. Representative substituted alkoxygroups may be substituted one or more times with substituents such asthose listed above, such as methoxymethyl and fluoromethoxy.

As used herein, “treating” or “treatment” of a disease in a patientrefers to (1) preventing the symptoms or disease from occurring in ananimal that is predisposed or does not yet display symptoms of thedisease; (2) inhibiting the disease or arresting its development; or (3)ameliorating or causing regression of the disease or the symptoms of thedisease. As understood in the art, “treatment” is an approach forobtaining beneficial or desired results, including clinical results. Forthe purposes of this technology, beneficial or desired results caninclude one or more, but are not limited to, alleviation or ameliorationof one or more symptoms, diminishment of extent of a condition(including a disease), stabilized (i.e., not worsening) state of acondition (including disease), delay or slowing of condition (includingdisease), progression, amelioration or palliation of the condition(including disease), states and remission (whether partial or total),whether detectable or undetectable. In one aspect, the term treatmentexcludes prevention or prophylaxis.

An animal, subject or patient for diagnosis or treatment refers to ananimal such as a mammal, or a human, ovine, bovine, feline, canine,equine, simian, etc. Non-human animals subject to diagnosis or treatmentinclude, for example, simians, murine, such as, rat, mice, canine,leporid, livestock, sport animals, and pets. In one aspect, the subjectis a human. It is to be understood that the terms “subject” and“patient” are interchangeable.

An “effective amount” is an amount sufficient to effect beneficial ordesired results. An effective amount can be administered in one or moreadministrations, applications or dosages. Such delivery is dependent ona number of variables including the time period for which the individualdosage unit is to be used, the bioavailability of the therapeutic agent,the route of administration, etc. It is understood, however, thatspecific dose levels of the therapeutic agents disclosed herein for anyparticular subject depends upon a variety of factors including theactivity of the specific compound employed, bioavailability of thecompound, the route of administration, the age of the animal and itsbody weight, general health, sex, the diet of the animal, the time ofadministration, the rate of excretion, the drug combination, and theseverity of the particular disorder being treated and form ofadministration. In general, one will desire to administer an amount ofthe compound that is effective to achieve a serum level commensuratewith the concentrations found to be effective in vivo. Theseconsiderations, as well as effective formulations and administrationprocedures are well known in the art and are described in standardtextbooks. Consistent with this definition and as used herein, the term“therapeutically effective amount” is an amount sufficient to treat aspecified disorder or disease or alternatively to obtain apharmacological response.

The term “pharmaceutically acceptable” as used herein refers to thatwhich is safe and sufficiently non-toxic for administration to asubject. By way of non-limiting example, some pharmaceuticallyacceptable salt or ester that are contemplated for use in connectionwith the present invention include those formed with an inorganic base,organic base, inorganic acid, organic acid, or amino acid (basic oracidic amino acid). Salts of inorganic bases can be, for example, saltsof alkali metals such as sodium or potassium; alkaline earth metals suchas calcium and magnesium or aluminum; and ammonia. Salts of organicbases can be, for example, salts trimethylamine, triethylamine,pyridine, picoline, ethanolamine, diethanolamine, and triethanolamine.Salts of inorganic acids can be, for example, salts of hydrochloricacid, hydroboric acid, nitric acid, sulfuric acid, and phosphoric acid.Salts of organic acids can be, for example, salts of formic acid, aceticacid, trifluoroacetic acid, fumaric acid, oxalic acid, lactic acid,tartaric acid, maleic acid, citric acid, succinic acid, malic acid,methanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid.Quaternary ammonium salts can be formed, for example, by reaction withlower alkyl halides, such as methyl, ethyl, propyl, and butyl chlorides,bromides, and iodides, with dialkyl sulphates, with long chain halides,such as decyl, lauryl, myristyl, and stearyl chlorides, bromides, andiodides, and with aralkyl halides, such as benzyl and phenethylbromides. Amino acid salts can be, for example, salts of glycine,alanine, arginine, asparagine, aspartic acid, cysteine, glutamine,glutamic acid, histidine, isoleucine, leucine, lysine, methionine,phenylalanine, serine, tryptophan, threonine, tyrosine, valine,citrulline, or ornithine.

As used herein, “protecting group” or “protective group” is used asknown in the art and as demonstrated in Greene, Protective Groups inOrganic Synthesis.

As used herein, “hydroxyl protective group” or “hydroxy protectinggroup” or “hydroxyl blocking group” refers to the generally understooddefinition of an alcohol or hydroxy protecting group as defined in T. W.Greene, Protective Groups in Organic Synthesis, John Wiley and Sons,1991 (hereinafter “Greene, Protective Groups in Organic Synthesis”).

As used herein, “acid protective group” or “acid protecting group” or“carboxylic acid blocking group” refers to the generally understooddefinition of protection for the carboxylic acid group as defined in T.W. Greene, Protective Groups in Organic Synthesis, John Wiley and Sons,1991 (hereinafter “Greene, Protective Groups in Organic Synthesis”).

As used herein, “amine protective group” or “amine protecting group”refers to the generally understood definition of protection for theamino group as defined in T. W. Greene, Protective Groups in OrganicSynthesis, John Wiley and Sons, 1991 (hereinafter “Greene, ProtectiveGroups in Organic Synthesis”).

As used herein, “an alcohol protecting group” or “alcohol protectivegroup” is a functional group that protects the alcohol group fromparticipating in reactions that are occurring in other parts of themolecule. Suitable alcohol protecting groups are well known to those ofordinary skill in the art and include those found in T. W. Greene,Protecting Groups in Organic Synthesis, John Wiley & Sons, Inc. 1981,the entire teachings of which are incorporated herein by reference.Exemplary alcohol protecting groups include, but are not limited to,actetyl, benzoyl, benzyl, p-methoxyethoxymethyl ether, methoxymethylether, dimethoxytrityl, p-methoxybenzyl ether, trityl, silyl ether(e.g., trimethylsilyl (TMS), tert-butyldimethylsilyl (TBMDS),tert-butyldimethylsilyloxymethyl (TOM) or triisopropylsilyl (TIPS)ether), tetrahydropyranyl (THP), methyl ether and ethoxyethyl ether(EE). In some embodiments, the terms “hydroxy protecting group” and“alcohol protecting group” are used interchangeably.

As used herein, substantially pure compound or isomer refers to oneisomer being 90% of the resulting isomeric mixture, or preferably 95% ofthe resulting isomeric mixture, or more preferably 98% of the resultingisomeric mixture, or even more preferably 99% of the resulting isomericmixture, and most preferably above 99% of the resulting isomericmixture.

Abbreviations: The following abbreviations are used in this disclosure:

-   CDI: 1,1′-carbonyldiimidazole-   DBU: 1,8-diazabicyclo[5.4.0]undec-7-ene;-   DCM: dicloromethane;-   DCE: dicloroethane;-   EDCl/EDC: 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide;-   EtOAc: ethyl acetate;-   HCl: hydrogen chloride;-   MeOH: methanol;-   TBAF: tetrabutylammonium fluoride;-   TBDMS: tert-butyl dimethylsilyl;-   TEA: triethylamine;-   TMSE: trimethylsilyl ether-   THF: tetrahydrofuran.

Compounds

Esuberaprost has the following chemical formula:

The present inventors have developed novel prodrugs of esuberaprost. Thephrase “prodrug(s) of esuberaprost” (also referred to “esuberaprostprodrug(s)” or just “prodrug(s)” depending on context) as used hereinrefers to any derivative of esuberaprost that converts in whole or inpart to esuberaprost in vivo following administration.

In one aspect, the present technology relates to prodrugs ofesuberaprost. For example, the prodrug may be a compound having Formula(I), or a diastereomer, enantiomer or pharmaceutically acceptable saltof the compound of Formula (I):

-   -   wherein    -   R¹ and R² each independently represent H, C₁-C₆ alkyl, —CO₂R⁶,        —CONR⁶R⁷, —P(O)(OH)₂—, —(CH₂)₂OP(O)(OH)₂— or a hydroxy        protecting group, or wherein OR′ or OR² forms an ester of an        amino acid, or wherein R¹ and R² connected to carbonyl to make a        cyclic carbonate group, or wherein OR′ or OR² together form a        phosphate group;    -   R³ represents NR⁷R⁸, OR⁹, or NHSO₂R¹⁰;    -   R⁴ represents H or C₁₋₃ alkyl;    -   R⁵, R⁶ and R⁷ each independently represent H or C₁₋₆ alkyl, or        wherein R⁶ and R⁷ together with the nitrogen to which they are        attached form a piperidine or a bipiperidine ring;    -   R⁸ represents H, optionally substituted C₁-C₆ alkyl, or

-   -   or wherein R⁷ and R⁸ are such that NR⁷R⁸ is an amide of an amino        acid;    -   R⁹ represents H or C₁-C₆ alkyl, which may be optionally        substituted with a terminal hydroxyl or carboxy group; and    -   R¹⁰ represents H, optionally substituted C₁-C₆ alkyl, optionally        substituted C₆-C₁₀ aryl, optionally substituted C₃-C₈ heteroaryl        or optionally substituted heterocyclyl;    -   with a proviso that all of R¹, R² and R⁸ are not H.

Examples of C₁₋₆ alkyl include a linear or branched chain alkyl groupsuch as a methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, n-pentyl and n-hexyl. The alkyl group may besubstituted with at least one substituent selected from the groupconsisting of halogen, cyano, nitro, C₃-C₆ cycloalkyl, C₆-C₁₀ aryl,C₃-C₈ heteroaryl, C₁-C₃ alkoxy, C₂-C₁₄ disubstituted amino and a C₂-C₁₄disubstituted carbamoyl.

Examples of C₆-C₁₀ aryl include phenyl and naphthyl. Examples of C₃-C₈heteroaryl include pyrrolyl, furyl, thienyl, oxazolyl, isoxazolyl,thiazolyl, purine, imidazolyl, pyridyl, pyridazyl, pyrimidyl,benzofuryl, indolyl, quinolyl, and quinazolyl. The heteroaryl group maybe substituted with at least one substituent selected from the groupconsisting of C₁-C₄ alkyl, benzyl, C₆-C₁₀ aryl, halogen, C₁-C₃ alkoxy,nitro, cyano and C₂-C₁₄ disubstituted amino group.

The heterocyclyl group may be saturated or partially unsaturated 3- to11-membered heterocyclyl ring containing one to four heteroatomsindependently selected from the group consisting of O, N and S. Examplesof heterocyclyl group include pyrrolidine, tetrahydrofuran, piperidine,morpholine, piperazine, dioxolane, dioxane and dihydropyranyl. Theheterocyclyl group may be substituted with at least one substituentselected from the group consisting of halogen, hydroxy, cyano, nitro,C₃-C₆ cycloalkyl, C₆-C₁₀ aryl, C₃-C₈ heteroaryl, C₁-C₃ alkoxy, andC₂-C₁₄ disubstituted amino.

Examples of halogen include F, Cl, Br and I. Examples of C₃-C₆cycloalkyl include cylopropyl, cyclopentyl and cyclohexyl. Examples ofC₁-C₃ alkoxy include methoxy, ethoxy and propoxy. Examples of C₁-C₃alkylthio include methylthio, ethylthio and propylthio. Examples ofC₆-C₁₄ arylthio include phenylthio and naphthylthio. Examples of C₂-C₁₄disubstituted amino include dimethylamino, diethylamino,diisopropylamino, diphenylamino, dibenzylamino and methylbenzylamino.Examples of the C₂-C₁₄ disubstituted carbamoyl includedimethylcarbamoyl, diethylcarbamoyl, dibenzylcarbamoyl andbenzylmethylcarbamoyl.

Amino acid(s) may include a D-isomer amino acid or an L-isomer aminoacid. In certain embodiments, an amino acid may be a naturally occurringamino acid. Yet, in some embodiments, an amino acid may be an artificialamino acid. Examples of amino acids include, but not limited to,carbamic acid, glycine, alanine, valine, leucine, isoleucine,methionine, proline, phenylalanine, tryptophan, serine, threonine,asparagine, glutamine, tyrosine, cysteine, lysine, arginine, histidine,asparatice acid, glutamic acid.

In some embodiments, R³ may be OH. In such a case, in certainembodiments, each of R¹ and R² may be each independently selected fromthe group consisting of H, —CO₂R⁶, —CONR⁶R⁷, —P(O)(OH)₂,—(CH₂)₂OP(O)(OH)₂, —C(O)-piperadine, and —C(O)-bipiperadine. R¹ and R²may be the same or different. For example one of R¹ and R² may be H andthe other may be selected from the group consisting of H, —CO₂R⁶,—CONR⁶R⁷, —P(O)(OH)₂, —(CH₂)₂OP(O)(OH)₂, —C(O)-piperadine, and—C(O)-bipiperadine. In some embodiments, OR′ or OR² forms an ester of anamino acid. In some embodiments, OR′ or OR² together form a phosphategroup. In some embodiments, le and R² connected to carbonyl to make acyclic carbonate group.

In some embodiments, when R³ is OH, at least one R¹ and R² may be—CO₂R⁶. In such a case, R⁶ may be selected from H and C₁₋₆ alkyl, suchas methyl. In certain embodiments, both of R¹ and R² may be —CO₂R⁶. Incertain other embodiments, one of R¹ and R² may be —CO₂R⁶ and the othermay be H. In such a case, R⁶ may be methyl.

In some embodiments, when R³ is OH, le and R² may be —CONR⁶R⁷. In such acase, each of R⁶ and R⁷ may be independently selected from H and C₁₋₄alkyl, such as methyl. In some embodiments, R⁶ and R⁷ may be the same.For example, in some embodiments, both of R⁶ and R⁷ may be H or both ofR⁶ and R⁷ may be methyl. Yet in some embodiments, R⁶ and R⁷ may bedifferent. For example, one of R⁶ and R⁷ may be H, while the other maybe methyl. In certain embodiments, R⁶ and R⁷ together with the nitrogento which they are attached form a piperidine ring. In certain otherembodiments, R⁶ and R⁷ together with the nitrogen to which they areattached form a bipiperidine ring.

In some embodiments, when R³ is OH, at least one R¹ and R² may be—(CH₂)₂OP(O)(OH)₂—. In certain embodiments, both of R¹ and R² may be—(CH₂)₂OP(O)(OH)₂—. In certain other embodiments, one of R¹ and R² maybe —(CH₂)₂OP(O)(OH)₂— and the other may be H.

In some embodiments, when R³ is OH, at least one R¹ and R² may bephosphate (—P(O)(OH)₂—). In certain embodiments, both of R¹ and R² maybe phosphate. In certain other embodiments, one of R¹ and R² may bephosphate and the other may be H.

In some embodiments, when R³ is OH, R¹ and R² are connected to carbonylto make a cyclic carbonate group. In certain other embodiments, when R³is OH, OR′ or OR² together form a phosphate group.

In some embodiments, when R³ is OH, at least one R¹ and R² may be anamino acid selected from the group consisting of glycine, alanine,arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid,histidine, isoleucine, leucine, lysine, methionine, phenylalanine,serine, tryptophan, threonine, tyrosine, valine, citrulline, andornithine. In certain embodiments, both of R¹ and R² may be an aminoacid. In certain other embodiments, one of R¹ and R² may be an aminoacid and the other may be H.

In some embodiments, when R¹ and R² each independently represent H orhydroxyl protecting group. In such case, in certain embodiments, R³represents NR⁷R⁸, OR⁹, or NHSO₂R¹⁰.

In some embodiments, when R¹ and R² are H or hydroxy protecting group,R³ is NR⁷R⁸. R⁷ may be H or C₁-C₆ alkyl. R₈ may be

R⁶ may be H or C₁-C₆ alkyl and R⁹ may be H or C₁-C₆ alkyl, which may beoptionally substituted with a terminal hydroxy or carboxy group. Incertain embodiments, R⁷ and R⁸ are such that NR⁷R⁸ may form an amide ofan amino acid.

In certain embodiments, R⁷ may be H. In such case, in some embodiments,R⁸ may be

where R⁹ may be H and R⁶ may be methyl.

In some embodiments, when R¹ and R² are H or hydroxyl protecting group,R³ is NHSO₂R¹⁰. In such case, in some embodiments, R¹⁰ may be selectedfrom the group consisting of optionally substituted C₁-C₆ alkyl,optionally substituted C₆-C₁₀ aryl, optionally substituted C₃-C₈heteroaryl or optionally substituted heterocyclyl group.

In some embodiments, when R¹ and R² are H and R³ is NHSO₂R¹⁰, R′° may beC₁₋₄ alkyl, such as methyl or ethyl. In other embodiments, when R¹ andR² are H and R³ is NHSO₂R¹⁰, R¹⁰ may be C₆₋₁₀ aryl, such as phenyl ornaphthyl. In certain cases, R¹⁰ may be C₆₋₁₀ aryl which may besubstituted with substituents as defined above.

In some embodiments, when R¹ and R² are H and R³ is an amino acidselected from the group consisting of glycine, alanine, arginine,asparagine, aspartic acid, cysteine, glutamine, glutamic acid,histidine, isoleucine, leucine, lysine, methionine, phenylalanine,serine, tryptophan, threonine, tyrosine, valine, citrulline, andornithine.

In some embodiments, when R² is H and R³ is OH, le is selected from thegroup consisting of H, CO₂CH₃, CONHCH₃, (CH₂)₂OP(O)(OH)₂, P(O)(OH)₂,

and an amino acid.

In some embodiments, when R¹ is H and R³ is OH, R² is selected from thegroup consisting of H, CO₂CH₃, CONHCH₃, (CH₂)₂OP(O)(OH)₂, P(O)(OH)₂,

and an amino acid.

In some embodiments, the prodrug may be a compound having one of thefollowing formulas:

In some embodiments, the prodrug can be an esuberaprost derivative withone or more hydroxyl groups or the carboxylic acid group of theesuberaprost structure modified, but which can be converted in vivo intoactive esuberaprost following administration and subsequent diffusioninto the blood. In some embodiments, the prodrug of esuberaprost iscompletely or substantially converted in vivo to esuberaprost outsidethe subcutaneous space, such as in the bloodstream. Preferred prodrugsinclude the compounds of Formula I above. Other preferred prodrugs ofesuberaprost include amide, carbonate, or carbamate esters ofesuberaprost. These prodrugs may have one or more advantages compared toesuberaprost or a salt thereof. For example, some of these prodrugs mayhave improved stability or greater tolerance in at least some patientpopulations.

In some embodiments, the prodrug of esuberaprost has greater than 50%,75%, 85%, 90%, 95%, or 98% conversion to esuberaprost in vivo followingadministration. In some embodiments, this conversion takes place in 15minutes, 30 minutes, 45 minutes, 1 hour, 2 hour, or 3 hours followingadministration. Prodrugs of esuberaprost include pharmaceuticallyacceptable salts of such prodrugs.

Preferably, the prodrugs of esuberaprost are stable during storage, forexample, by not hydrolyzing into esuberaprost spontaneously in asolution before administering or during initial injection and at thesite of injection. Preferably, the prodrug formulations of the presentinvention are free of esuberaprost or substantially free of esuberaprostin free acid form. In some embodiments, less than 10%, 5%, 2%, 1%, or0.1% of the prodrug of esuberaprost converts to esuberaprost during adefined storage period. In some embodiments, that defined storage periodcan be 1, 2, 3, 6, or 12 months.

Pharmaceutical Compositions

Esuberaprost prodrugs of the present technology may be provided in aform of a pharmaceutical composition, which may also comprise apharmaceutically acceptable carrier, excipient, binder, diluent or thelike. Such pharmaceutical composition may be manufactured by methodsknown in the art such as granulating, mixing, dissolving, encapsulating,lyophilizing, emulsifying or levigating processes, among others. Thecomposition may be in the form of, for example, granules, powders,tablets, capsules, syrup, suppositories, injections, emulsions, elixirs,suspensions and solutions. The composition may be formulated for anumber of different administration routes, such as, for oraladministration, transmucosal administration, rectal administration,transdermal or subcutaneous administration, as well as intrathecal,intravenous, intramuscular, intraperitoneal, intranasal, intraocular orintraventricular injection. The esuberaprost prodrug may be administeredby any of the above routes, for example in a local rather than asystemic administration, including as an injection or as a sustainedrelease formulation.

In one embodiment, the pharmaceutical composition can compromise aprodrug of esuberaprost and a carrier, such as sterile water. In someembodiments, the prodrug of esuberaprost is formulated for subcutaneousadministration, and such formulation may or may not include m-cresol oranother preservative.

For oral, buccal, and sublingual administration, powders, suspensions,granules, tablets, pills, capsules, gelcaps, and caplets may beacceptable as solid dosage forms. These can be prepared, for example, bymixing one or more esuberaprost prodrugs, or pharmaceutically acceptablesalts thereof, with at least one additive or excipient such as a starchor other additive. Suitable additives or excipients may be sucrose,lactose, cellulose sugar, mannitol, maltitol, dextran, sorbitol, starch,agar, alginates, chitins, chitosans, pectins, tragacanth gum, gumarabic, gelatins, collagens, casein, albumin, synthetic orsemi-synthetic polymers or glycerides, methyl cellulose,hydroxypropylmethyl-cellulose, and/or polyvinylpyrrolidone. Optionally,oral dosage forms may contain other ingredients to aid inadministration, such as an inactive diluent, or lubricants such asmagnesium stearate, or preservatives such as paraben or sorbic acid, oranti-oxidants such as ascorbic acid, tocopherol or cysteine, adisintegrating agent, binders, thickeners, buffers, sweeteners,flavoring agents or perfuming agents. Additionally, dyestuffs orpigments may be added for identification. Tablets may be further treatedwith suitable coating materials known in the art.

Liquid dosage forms for oral administration may be in the form ofpharmaceutically acceptable emulsions, syrups, elixirs, suspensions,slurries and solutions, which may contain an inactive diluent, such aswater. Pharmaceutical formulations may be prepared as liquid suspensionsor solutions using a sterile liquid, such as, but not limited to, anoil, water, an alcohol, and combinations of these. Pharmaceuticallysuitable surfactants, suspending agents, emulsifying agents, may beadded for oral or parenteral administration.

As noted above, suspensions may include oils. Such oil include, but arenot limited to, peanut oil, sesame oil, cottonseed oil, corn oil andolive oil. Suspension preparation may also contain esters of fatty acidssuch as ethyl oleate, isopropyl myristate, fatty acid glycerides andacetylated fatty acid glycerides. Suspension formulations may includealcohols, such as, but not limited to, ethanol, isopropyl alcohol,hexadecyl alcohol, glycerol and propylene glycol. Ethers, such as butnot limited to, poly(ethyleneglycol), petroleum hydrocarbons such asmineral oil and petrolatum; and water may also be used in suspensionformulations.

Injectable dosage forms generally include aqueous suspensions or oilsuspensions which may be prepared using a suitable dispersant or wettingagent and a suspending agent. Injectable forms may be in solution phaseor in the form of a suspension, which is prepared with a solvent ordiluent. Acceptable solvents or vehicles include sterilized water,Ringer's solution, or an isotonic aqueous saline solution.Alternatively, sterile oils may be employed as solvents or suspendingagents. Preferably, the oil or fatty acid is non-volatile, includingnatural or synthetic oils, fatty acids, mono-, di- or tri-glycerides.

For injection, the pharmaceutical formulation may be a powder suitablefor reconstitution with an appropriate solution as described above.Examples of these include, but are not limited to, freeze dried, rotarydried or spray dried powders, amorphous powders, granules, precipitates,or particulates. For injection, the formulations may optionally containstabilizers, pH modifiers, surfactants, bioavailability modifiers andcombinations of these. The compounds may be formulated for parenteraladministration by injection such as by bolus injection or continuousinfusion. A unit dosage form for injection may be in ampoules or inmulti-dose containers. Besides those representative dosage formsdescribed above, pharmaceutically acceptable excipients and carries aregenerally known to those skilled in the art and are thus included in theinstant invention. Such excipients and carriers are described, forexample, in “Remingtons Pharmaceutical Sciences” Mack Pub. Co., NewJersey (1991), which is incorporated herein by reference.

An esuberaprost prodrug may be formulated in a formulation suitable forparenteral administration that may comprise sterile aqueous preparationsof an esuberaprost prodrug, or a pharmaceutically acceptable saltthereof, where the preparations may be isotonic with the blood of theintended recipient. These preparations may be administered by means ofsubcutaneous injection, although administration may also be effectedintravenously or by means of intramuscular or intradermal injection.Such preparations may conveniently be prepared by admixing the compoundwith water or a glycine or citrate buffer and rendering the resultingsolution sterile and isotonic with the blood.

In some embodiments, a formulation of an esuberaprost prodrug forparenteral administration, such as intravenous infusion or subcutaneousinfusion (including continuous subcutaneous infusion), may be preparedby admixing the prodrug with a vehicle, such as a buffer. In certainembodiments, the vehicle may be a phosphate containing vehicle, i.e. atleast one phosphate salt, which may be for example, dibasic phosphate,such as sodium dibasic phosphate or potassium dibasic phosphate, ortribasic phosphate, such as sodium tribasic phosphate or potassiumphosphate. In certain embodiments, the vehicle may also contain ahalogen salt, such as a chloride salt, which may be, for example, sodiumchloride or potassium chloride. The halogen salt, such as sodiumchloride may be used to adjust tonicity of the vehicle. In certainembodiments, it may be preferred that a phosphate and a halogen salthave the same cation. For example, when a phosphate is sodium phosphate,such as sodium tribasic phosphate or sodium tribasic phosphate, ahalogen salt may a sodium halogen salt such as sodium chloride.Similarly, when a phosphate is potassium phosphate, such as potassiumtribasic phosphate or potassium tribasic phosphate, a halogen salt may apotassium halogen salt such as potassium chloride. A solvent in thevehicle may contain water. In certain embodiments, water may be the onlysolvent in the vehicle. Yet in certain embodiments, the vehicle maycontain one or more additional solvent in addition to water. In someembodiments, an additional solvent may be a preservative, such asm-cresol.

Preferably, the vehicle is isotonic with blood of a patient, such as ahuman being. The term isotonic may mean that the osmolarity and ionconcentrations of the vehicle match those of the patient, such as humanbeing. Non-limiting example of vehicles include phosphate-bufferedsaline, which is a water based salt solution containing disodiumhydrogen phosphate, sodium chloride and, in some formulations, potassiumchloride and potassium dihydrogen phosphate. Other examples may includea vehicle containing 20 mM disbasic sodium phosphate with 125 mM sodiumchloride and a vehicle containing 15 mM sodium phosphate tribasic, 125mM sodium chloride and 0.3% w/w m-cresol.

In certain embodiments, an esuberaprost prodrug may be administeredsubcutaneously. In some embodiments, the subcutaneous administration maybe continuous subcutaneous infusion, such as continuous subcutaneousinfusion by an infusion pump, which is preferably portable orimplantable.

Therapeutic Methods

The esuberaprost prodrugs may be used for one or more of the samepurposes for which esuberaprost is known to be useful, such as fortreating a condition, for which esuberaprost is known to be effective.For example, the esuberaprost prodrugs may be used for administering toa subject in need thereof, such as a human being, for treating a diseaseor disorder, which may be treated with esuberaprost, such as pulmonaryhypertension (including primary and secondary pulmonary hypertension andpulmonary arterial hypertension), peripheral vascular disease, severeintermittent claudication, critical limb ischemia, ischemic lesions,asthma, pulmonary fibrosis, diabetic neuropathic foot ulcers,interstitial lung disease. For therapeutic purposes, such as treatingpulmonary hypertension, an esuberaprost prodrug may be administered to asubject, such a human being, in a therapeutically effective amount,which may be an amount of the esuberaprost prodrug, which is sufficientto ameliorate one or more symptoms of a disease or disorder, which maybe treated with esuberaprost, such as pulmonary hypertension.

Accordingly, provided herein is a method of treating a disease orcondition in a patient in need thereof comprising administering to thepatient an effective amount of a prodrug of esuberaprost. In at leastone embodiment, the disease or condition is one or more selected fromthe group consisting of pulmonary hypertension, congestive heartfailure, peripheral vascular disease, Raynaud's phenomenon, Scleroderma,renal insufficiency, peripheral neuropathy, digital ulcers, intermittentclaudication, ischemic limb disease, peripheral ischemic lesions,pulmonary fibrosis and asthma. In at least one embodiment, providedherein is a method of treating pulmonary hypertension comprising,administering subcutaneously to a patient suffering from pulmonaryhypertension an effective amount of a prodrug of esuberaprost. In atleast one embodiment, provided herein is a method of treating vasculardisease comprising, administering subcutaneously to a patient sufferingfrom vascular disease an effective amount of a prodrug of esuberaprost.In some embodiments, provided herein are methods of treating one or moreof pulmonary hypertension and vascular disease comprising, administeringsubcutaneously to a patient suffering from vascular disease an effectiveamount of a compound of Formula (I).

Methods of Preparation

In one aspect, processes are providing for preparing prostacyclinderivatives. Such derivatives may in some embodiments, include prodrugsof esuberaprost. The processes also include the preparation of a numberof intermediate compounds useful in the preparation of prostacyclinderivatives. In one aspect, a process is provided to produce apharmaceutical compound represented by the general Formula (I), Formula(III), Formula (VI), Formula (VIII), Formula (XI) or Formula (XIV). Insome embodiments, a process is provided to produce a pharmaceuticalcompound represented by the general Formula (I), Formula (III), Formula(VI), Formula (VIII), Formula (XI) or Formula (XIV) in a substantiallyisomerically pure form. The process is completed in fewer steps than theknown synthetic methods, and may be conducted to prepare commerciallyuseful quantities. In another aspect, synthetic methods are provided forproducing prodrugs of esuberaprost, which are stereoselective,efficient, scalable and economical. In another aspect, substantiallyisomerically pure compounds and intermediates are produced by the aboveprocesses.

In one embodiment, the present technology relates to a new process forthe preparation of esuberaprost prodrugs. The process is a much moreefficient, commercially viable process to manufacture the targetcompounds. In other embodiments, novel synthetic intermediate compoundsuseful for the synthesis of esuberaprost prodrugs are provided.

In one embodiment, the present technology provides a process for thepreparation of a compound of Formula (III):

-   -   comprising:    -   (a) reacting a compound of Formula (II)

-   -   with methanesulfonic acid, optionally in the presence of at        least one carboxyl-activating agent, optionally in the presence        of at least one suitable coupling agent, to form a compound of        Formula (II′)

-   -   (b) deprotecting the product of Formula (II′) of step (a) in        acidic condition to form the compound of Formula (III).

In one embodiment, the present technology provides a process for thepreparation of a compound of Formula (VI):

-   -   comprising:    -   (a) reacting a compound of Formula (IV)

-   -   with 4-nitrophenyl chloroformate, optionally in the presence of        excess of at least one amine base to form a compound of Formula        (V);

-   -   (b) desilylating the compound of Formula (V) of step (a) to form        the compound of Formula (VI).

In one embodiment, the present technology provides a process for thepreparation of a compound of Formula (VIII):

-   -   comprising:    -   (a) reacting a compound of Formula (IV)

-   -   with methyl chloroformate, optionally in the presence of at        least one amine base to form a compound of Formula (VII);

-   -   (b) desilylating the compound of Formula (VII) of step (a) to        form the compound of Formula (VIII).

In one embodiment, the present technology provides a process for thepreparation of a compound of Formula (XI):

-   -   comprising:    -   (a) reacting a compound of Formula (IX)

-   -   with glycine methyl ester hydrochloride, optionally in the        presence of at least one carboxyl-activating agent, optionally        in the presence of at least one amine base to form a compound of        Formula (X);

-   -   (b) hydrolyzing the ester of Formula (X) of step (a) to form the        compound of Formula (XI).

In one embodiment, the present technology provides a process for thepreparation of a compound of Formula (XIV):

-   -   comprising:    -   (a) reacting a compound of Formula (IV)

-   -   with carbonyldiimidazole to form a compound of Formula (XII);

-   -   (b) reacting a compound of Formula (XII) with piperidine to form        a compound of Formula (XIII);

-   -   (c) desilylating the compound of Formula (XIII) of step (b) to        form the compound of Formula (XIV).

As noted above, the reactions in the process of preparation ofesuberaprost prodrugs may be conducted in the presence of suitablecarboxyl-activating agents, coupling agents, deprotecting agents,desilylating agents, hydrolyzing agents, acids, bases and solvents.Suitable carboxyl-activating agents include, but are not limited to1,1′-carbonyldiimidazole (CDI),1-ethyl-3-(3′-dimethylaminopropyl)carbodiimide hydrochloride (EDCl),1,3-dicyclohexylcarbodiimide (DCC),benzotriazol-1-yl-oxy-tris(dimethylamino)phosphonium hexafluorophosphate(BOP), and 1,3-Diisopropylcarbodiimide (DICD). Suitable coupling agentsinclude, but are not limited to 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)and tetramethyluronium hexafluorophosphate (HBTU). Suitable basesinclude for example, amine bases such as pyridine,N,N,N′N′-tetramethylethylenediamine (TMEDA), dimethylamine (DMA),diethylamine (DEA) and trimethylamine (TEA). Suitable acids include forexample, acetic acid, hydrochloric acid and sulfuric acid.

Suitable hydrolyzing agents for removal of the carboxylic acidprotective group include, but are not limited to lithium hydroxide,barium hydroxide, sodium hydroxide, potassium hydroxide, calciumhydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate,trimethyltin hydroxide, tributyltin hydroxide, palladium-carbon inpresence of hydrogen under basic conditions, and the like, andcombinations thereof. In some embodiments, the hydrolyzing agent istrimethyltin hydroxide.

Hydroxy protecting groups can be removed by acid or base catalysedhydrolysis or catalytic hydrogenolysis. For example, tetrahydropyarnyl(THP) ether protecting group may be removed, for example, by acidhydrolysis, silyl ethers may require hydrogen fluoride ortetrabutylammonium fluoride to be cleaved and benzyl ether protectinggroup may be removed, for example, by hydrogenolysis.

The deprotection reaction of t-butyldimethylsilyl group (TBDMS) and/ortrimehtyl silyl ester group (TMSE) can be conducted under relativelymild conditions using acids such as hydrochloric acid, optionally with asolvent such as methanol or ethanol; or fluoride ions, in the form ofinorganic salts such as KF, LiBF₄ or NH₄F, or an organic salt such astetrabutylammonium fluoride (TBAF), optionally with a solvent such asTHF. In at least one embodiment, the deprotection is conducted in thepresence of HCl in methanol. In at least one embodiment, thedeprotection (e.g., desilylation) is conducted in the presence of TBAFin THF.

Suitable solvents used in the include, but are not limited to, analcohol, e.g., methanol, ethanol, isopropyl alcohol, 1-propanol,1-butanol, 2-butanol, a ketone, e.g., acetone, ethyl methyl ketone,methyl isobutyl ketone, a hydrocarbon, e.g., toluene, xylene, hexanes,heptanes, cyclohexane, a halogenated hydrocarbon, e.g., dichloromethane(DCM), ethylene dichloride, chloroform, an ester, e.g., ethyl acetate,n-propyl acetate, n-butyl acetate, t-butyl acetate, an ether, e.g.,diethyl ether, diisopropyl ether, methyl t-butyl ether, tetrahydrofuran(THF), dioxane, a polar aprotic solvent, e.g., N,N-dimethylformamide,N,N-dimethylacetamide, dimethylsulfoxide, sulfolane,N-methylpyrrolidone, a nitrile, e.g., acetonitrile, propionitrile,water; or mixtures thereof. In some embodiments, the process isconducted in one or more solvents selected from the group consisting oftetrahydrofuran, methanol, dichloromethane, dichloroethane, and water.In some embodiments, the organic solvents such as DCM, DCE, THF andmethanol are anhydrous. In at least one embodiment, the solvent ismethanol. In at least one embodiment, the solvent is THF. In at leastone embodiment, the solvent is DCM.

Esuberaprost prodrugs may be prepared according to methods described inthe synthetic schemes below.

Scheme 1 illustrates synthesis of methanesulfonamide Prodrug 3 (III).This synthesis may start with di-TBDMS protected esuberaprost reactedwith NH₂SO₂CH₃ to form a protected sulfonamide compound, which can bedeprotected to provide the methanesulfonamide Prodrug 3 (III). As shownin Scheme 1, esuberaprost methanesulfonamide (3) was synthesized fromdi-TBDMS esuberaprost (1). The starting di-TBDMS esuberaprost (1) wasprepared from pure esuberaprost in three steps. The activation of acid(1) with CDI followed by reaction with methanesulfonamide in thepresence of DBU gave di-TBDMS esuberparost methanesulfonamide (2) andwas purified by silica gel column chromatography. The deprotection ofTBDMS from sulfonamide (2) using hydrogen chloride in methanol affordedthe desired esuberaprost methanesulfonamide (3) after chromatography.This prodrug (3) was characterized by spectral data (IR, ¹H NMR, ¹³C NMRand MS).

As shown in Scheme 2, esuberaprost side chain N,N-dimethyl carbamate (6)was synthesized from TBDMS esuberaprost TMSE ester (4). The TMSE ester(4) was prepared from mono-TBDMS protected esuberaprost acid. The ester(4) was treated with 4-nitrophenyl chloroformate to give 4-nitrophenylcarbonate. The carbonate, without isolation, was treated withdimethylamine in tetrahydrofuran to afford protected dimethyl carbamate(5) after chromatography. The desilylation of compound (5) withtetrabutylammonium fluoride (TBAF) in tetrahydrofuran gave esuberaprostN,N-dimethyl carbamate (6). This prodrug (6) was characterized byspectral data (IR, ¹H NMR, ¹³C NMR and MS).

As shown in Scheme 3, esuberaprost side chain methyl carbamate (8) wasalso synthesized from TBDMS esuberaprost TMSE ester (4). The methylcarbonate (7) was synthesized from TMSE ester (4) by treating withmethyl chloroformate in the presence ofN,N,N′N′-tetramethylethylenediamine (TMEDA) in dichloromethane at −70°C. in good yield. The desilylation of compound (7) withtetrabutylammonium fluoride (TBAF) in tetrahydrofuran affordedesuberaprost side chain methyl carbonate (8). This prodrug (8) wascharacterized by spectral data (IR, ¹H NMR, ¹³C NMR and MS).

As shown in Scheme 4, esuberaprost glycine amide (11) was synthesizedfrom esuberaprost (9). The esuberaprost (4) was treated with glycinemethyl ester hydrochloride in the presence of EDCl.HCl and triethylamineto give amido methyl ester (10). The ester (10) was hydrolyzed withtrimethyltin hydroxide to afford the desired esuberaprost glycine amide(11). The prodrug (11) was characterized was characterized by spectraldata (¹H NMR and MS).

As shown in Scheme 5, esuberaprost side chain piperidine carbamate (14)was synthesized from TBDMS esuberaprost TMSE ester (4). The TBDMSesuberaprost TMSE ester (4) was reacted with carbonyldiimidazole (CDI)to obtain carbonylimidazole derivative (12). The activated compound 12was reacted with piperidine in the presence of water and tetrahydrofuranto obtain piperidine side chain carbamate (13). The TBDMS and TMSEprotecting groups of carbamate intermediate (14) were cleaved usingtetrabutylammonium fluoride (TBAF) to obtain esuberaprost side chainpiperidine carbamate (14) and was characterized by spectral data (′HNMR, ¹³C NMR, LC-MS).

The present invention is further illustrated by, though in no waylimited to, the following examples.

Example 1: Synthesis of Di-TBDMS Esuberaprost Methanesulfonamide (2)

To a solution of di-TBDMS esuberaprost (1) (0.18 g, 0.287 mmol) inanhydrous tetrahydrofuran (2 mL) was added 1,1′-carbonyldiimidazole(CDI) (0.07 g, 0.432 mmol) in one portion at room temperature underargon. The clear reaction mixture was stirred at room temperature for 30min and then at 75° C. (oil bath temperature) for 30 min. The reactionmixture was cooled to room temperature and then methansulfonamide (0.082g, 0.862 mmol) was added in one portion. The reaction mixture wasstirred at room temperature until clear solution was obtained. To thisclear solution was added a solution of1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (0.22 g, 1.44 mmol) inanhydrous tetrahydrofuran (2 mL) under argon. After complete addition,the reaction mixture was stirred at room temperature for 2 h and thereaction was monitored by TLC (MeOH/CH₂Cl₂, 0.5:9.5). The reaction wasnot complete. The reaction mixture was continued to stir at roomtemperature overnight. After 17 h, the reaction was checked by tlc(MeOH/CH₂Cl₂, 0.5:9.5). The mixture was quenched with water (15 mL) andthen extracted with EtOAc (3×15 mL). The combined EtOAc extracts werewashed with water (3×15 mL), brine (1×10 mL), dried (Na₂SO₄), filteredand concentrated in vacuo to give white foamy sticky solid (0.187 g)(Lot #RD-UT-1204-147). The crude product was chromatographed on silicagel (230-400 mesh) (15 g) using CH₂Cl₂ and 1-8% MeOH/CH₂Cl₂ to givedi-TBDMS esuberaprost methanesulfonamide (2) as a white foamy stickysolid (0.13 g) (Lot #RD-UT-1204-147-C). The pure fraction of 2 (0.02 g)(Lot #RD-UT-1204-147-B) was fully characterized by spectral data (IR, ¹HNMR, ¹³C NMR, DEPT and MS).

TABLE 1 Materials used in Example 1 Name MW Lot No. Amount mmol Eq.Di-TBDMS esuberaprost (1) 627.02 RD-UT-  0.18 g 0.287 1.00 1161-075-B1,1′-Carbonyldiimidazole (CDI) 162.15 BCBR6489V  0.07 g 0.432 1.5Methanesulfonamide 95.12 BCBH0661V 0.082 g 0.862 3.01,8-Diazabicyclo[5.4.0]- 152.24 BCBR7994V  0.22 g 1.44 5.0 undec-7-ene(DBU) Tetrahydrofuran (anhydrous) NA SHBJ0753    4.0 mL NA NA Silica gel(230-400 mesh) NA TA2142885   15 g NA NA

The reaction in Example 1 is described in the scheme below:

Example 2: Synthesis of Esuberaprost Methanesulfonamide (3)

To a solution of di-TBDMS esuberaprost methanesulfonamide (2) (0.13 g,0.185 mmol) in anhydrous methanol (2 mL) was added a solution ofhydrogen chloride in methanol (1.25 M) (0.40 mL, 0.50 mmol) at roomtemperature under argon. The reaction mixture was stirred at roomtemperature for 3 h and checked by TLC (MeOH/CH₂Cl₂, 0.5:9.5 and 1:9).The reaction was complete. The argon was bubbled slowly through thereaction mixture for 2 min at room temperature to remove excess hydrogenchloride. Then, the mixture was evaporated in vacuo at 30° C. (waterbath temperature) to remove the organic volatiles to give crudesulfonamide product (3) as a pale yellow glassy viscous liquid (0.097 g)(Lot #RD-UT-1204-154). The crude product was chromatographed on silicagel (10 g) column using 25-100% EtOAc/Hexane and 5-10% MeOH/EtOAc togive esuberaprost methanesulfonamide (3) as a pale yellow viscous liquid(0.021 g) (Lot #RD-UT-1204-154-A) and (0.041 g) (Lot #RD-UT-1204-154-B).The compound was characterized by spectral data (IR, ¹H NMR, ¹³C NMR,DEPT and MS).

TABLE 2 Material used in Example 2 Name MW Lot No. Amount mmol Eq.Di-TBDM esuberaprost 703.14 RD-UT- 0.13 g  0.185 1.00 methansulfonamide(2) 1204-147-C Hydrogen chloride in 36.5 BCBT3427 0.40 mL 0.50 2.70methanol (1.25M) Methanol (anhydrous) NA 01949CJ   2 mL NA NA Silica gel(230-400 mesh) NA TA2142885  10 g NA NA

The reaction in Example 2 is described in the scheme below:

Example 3: Synthesis of TBDMS Esuberaprost TMSE Ester Side ChainN,N-Dimethyl Carbamate (5)

TBDMS esuberaprost TMSE ester (4) (100 mg, 0.16 mmol) and pyridine (38.7mg, 0.49 mmol) were dissolved in anhydrous THF (3 ml) at roomtemperature under argon. The solution was cooled to 0-5° C., and then4-nitrophenyl chloroformate (74.3 mg, 0.37 mmol) in THF (1 ml) was addeddropwise. The reaction mixture was stirred for 1.5 h and thendimethylamine (22 mg, 0.49 mmol) in THF (0.5 ml) was added. The reactionmixture was continued to stir at 0-5° C. for 1 h and checked TLC(EtOAc/Hexane 1:4), the reaction was complete. The reaction mixture wasconcentrated in vacuo to obtain crude product. The chromatography ofcrude product on silica gel using 0-20% EtOAc in hexane afforded desiredcarbamate (5) (103 mg) (Lot #RD-UT-1199-101A). The TBDMS esuberaprostTMSE ester side chain N,N-dimethyl carbamate (5) was characterized byspectral data (′H NMR and MS).

TABLE 3 Material used in Example 3 Name MW Lot No. Amount mmol Eq. TBDMSEsuberaprost 613.00 RD-UT- 100.0 mg 0.16 1.0 TMSE ester (4) 1199-079Pyridine 79.16 SHBH7698  38.7 mg 0.49 3.0 4-Nitrophenyl 201.56 WXBC1772V 74.3 mg 0.37 2.3 chloroformate Dimethylamine 45.08 SHBG-0756V  22.0 mg0.49 3.0 THE NA SHBJ0753  4.5 ml NA NA

The reaction in Example 3 is described in the scheme below:

Example 4: Synthesis of Esuberaprost Side Chain N,N-Dimethyl Carbamate(6)

The TBDMS esuberaprost TMSE ester side chain N,N-dimethyl carbamate (5)(98 mg, 0.14 mmol) was dissolved in anhydrous THF (10 ml) and TBAF (1.0M in THF) (0.86 ml, 0.86 mmol) was added dropwise at room temperatureunder argon with stirring. The progress of reaction was monitored by TLC(EtOAc/Hexane, 1:4, DCM/MeOH, 9:1). The reaction was stopped stirringafter 5 h and the solvent was evaporated in vacuo. The residue wasdissolved in EtOAc (8 ml) and washed with water (1×5 ml) and brine (2×5ml), then dried over Na₂SO₄ and concentrated in vacuo to give crudeproduct (203 mg). The chromatography of crude product on silica gel with0-5% MeOH in EtOAc gave desired product compound (6) (119 mg) (Lot#RD-UT-1199-103-1). The second chromatography of the product on silicagel with 0-5% methanol in DCM afforded the pure desired carbamate (6)(39 mg) (Lot #RD-UT-1199-103-2). The esuberaprost side chainN,N-dimethyl carbamate (6) was characterized by spectral data (¹H NMR,¹³C NMR, IR and MS).

TABLE 4 Material used in Example 4 Name MW Lot No. Amount mmol Eq.Alkenyl acetoxycyclo- 358.42 RD-UT- 14.2 g 39.61 1.0 pentabenzofuran (5)1137-178 Methanol (anhydrous) NA T-08-0195 150 mL NA NA DichloromethaneNA SHBF0333V 50 mL NA NA (anhydrous) Sodium borohydride 37.83 00000232812.99 g 79.23 2.0 Silica gel (230-400 mesh) NA 80107 622 g NA NA

The reaction in Example 4 is described in the scheme below:

Example 5: Synthesis of TBDMS Esuberaprost TMSE Ester Side Chain MethylCarbonate (7)

The TBDMS esuberaprost TMSE ester (4) (100 mg, 0.163 mmol) andN,N,N′,N′-tetramethylethylenediamine (38 mg, 0.33 mmol) were dissolvedin anhydrous DCM (5 ml), the solution was cooled to −70° C. and thenmethyl chloroformate (31 mg, 0.326 mmol) in anhydrous DCM (1 ml) wasadded dropwise under argon with stirring. The reaction mixture wasstirred for 2 h at this temperature and then at 0° C. for 2 h and theprogress of reaction was monitored by TLC (EtOAc/Hexane 1:4). Thereaction was not complete. The reaction mixture was re-cooled to −50° C.and additional methyl chloroformate (31 mg, 0.326 mmol) in DCM (1 ml)was added dropwise, then the reaction mixture was stirred for another 2h. The reaction was complete. The reaction mixture was quenched withwater (5 ml) and the organic layer was separated and washed with brine(2×3 ml), then dried over Na₂SO₄ and concentrated in vacuo to obtaincrude product. The chromatography of the crude product on silica gelusing 0-4% EtOAc in hexane afforded pure carbonate (7) (118 mg) (Lot#RD-UT-1199-104). The TBDMS esuberaprost TMSE ester side chain methylcarbonate (7) was characterized by spectral data CH NMR, ¹³C NMR, IR andMS).

TABLE 5 Material used in Example 5 Name MW Lot No. Amount mmol Eq. TRDNEsuberaprost 613.00 RD-UT- 100 mg 0.16 1.0 TMSE ester (4) 1199-079N,N,N′,N′-Tetramethyl 116.21 10201026  38 mg 0.33 7.0 ethylenediamine(TMEDA) diamine Methyl chloroformate 94.50 STBF9617V  62 mg 0.56 4.0 DCMNA 53200  5 ml NA NA (anhydrous)

The reaction in Example 5 is described in the scheme below:

Example 6: Synthesis of Esuberaprost Side Chain Methyl Carbonate (8)

The TBDMS esuberaprost TMSE ester side chain methyl carbonate (7) (110mg, 0.16 mmol) was dissolved in anhydrous THF (10 ml) and TBAF (1.0 M inTHF) (0.98 ml, 0.98 mmol) was added dropwise at room temperature underargon with stirring. The reaction was monitored by TLC (EtOAc/Hexane,1:4 and DCM/MeOH, 9:1). The reaction was stopped stirring after 1.5 hand the solvent was evaporated in vacuo. The residue was dissolved inEtOAc (8 ml) and washed with water (1×5 ml) and brine (2×5 ml), thendried over Na₂SO₄ and concentrated in vacuo to give crude product. Thechromatography of crude product on silica gel with 0-5% MeOH in DCMafforded desired carbonate (8) (76 mg) (Lot #RD-UT-1199-105). Theesuberaprost side chain methyl carbonate (8) was characterized byspectral data (¹H NMR, ¹³C NMR, IR and MS).

TABLE 6 Material used in Example 6 Name MW Lot No. Amount mmol Eq. TBDMSesuberaprost 671.03 RD-UT- 110 mg 0.16 1.0 TMSE ester side chain1199-101A methyl carbonate (7) TBAF (1.0M in THF) 261.47 09622CH 0.98ml  0.98 6.0 THF (anhydrous) NA SHBJ0753  10 ml NA NA

The reaction in Example 6 is described in the scheme below:

Example 7: Synthesis of Esuberaprost Glycine Amide Methyl Ester (10)

A 50 mL round bottom flask equipped with magnetic stir bar charged witha solution of esuberaprost (9) (0.95 g, 2.38 mmol) in anhydrous DCM (40mL) under argon. To this solution was added EDCl.HCl (0.68 g, 3.57 mmol)followed by glycine methyl ester hydrochloride (0.30 g, 2.38 mmol) atroom temperature under argon. The reaction mixture was stirred for 20min and then triethylamine (0.072 g, 7.14 mmol) was added. The progressof reaction was monitored by TLC (DCM/MeOH, 9:1). After 3 h, thereaction mixture was quenched with water (20 mL) and the pH was adjustedto 4-5 with 5% HCl. The DCM layer was separated and washed with water(20 mL), brine (20 mL), dried (Na₂SO₄), filtered and concentrated invacuo to obtain crude product. The crude product was purified on silicagel using a gradient solvent of 0-5% methanol in ethyl acetate to givepure esuberaprost glycine amide methyl ester (10) (0.55 g) (Lot#RD-UT-1199-017). The compound was characterized by spectral data (¹HNMR and MS).

TABLE 7 Material used in Example 7 Name MW Lot No. Amount mmol Eq.Esuberaprost (9) 398.49 RD-UT-1199-016 0.95 g 2.38 1.0 Glycine methyl125.55 STBD9571V 0.30 g 2.38 1.0 ester hydrochlotide EDCI. HCl 191.706XWHN LD 0.68 g 3.57 1.5 Triethylamine 101.19 SHBF6420V 0.72 g 7.14 3.0Dichloromethane NA 53200   40 ml NA NA (anhydrous)

The reaction in Example 7 is described in the scheme below:

Example 8: Synthesis of Esuberaprost Glycine Amide (11)

The TBDMS esuberaprost TMSE ester side chain methyl carbonate (7) (110mg, 0.16 mmol) was dissolved in anhydrous THF (10 ml) and TBAF (1.0 M inTHF) (0.98 ml, 0.98 mmol) was added dropwise at room temperature underargon with stirring. The reaction was monitored by TLC (EtOAc/Hexane,1:4 and DCM/MeOH, 9:1). The reaction was stopped stirring after 1.5 hand the solvent was evaporated in vacuo. The residue was dissolved inEtOAc (8 ml) and washed with water (1×5 ml) and brine (2×5 ml), thendried over Na₂SO₄ and concentrated in vacuo to give crude product. Thechromatography of crude product on silica gel with 0-5% MeOH in DCMafforded desired carbonate (8) (76 mg) (Lot #RD-UT-1199-105). Theesuberaprost side chain methyl carbonate (8) was characterized byspectral data CH NMR, ¹³C NMR, IR and MS).

TABLE 6 Material used in Example 6 Name MW Lot No. Amount mmol Eq.Esuberaprost glycine 469.25 RD-UT-  80.1 mg 0.17 1.0 amide methyl ester(10) 1199-017 Trimethyltinhydroxide 180.80 20205600 153.7 mg 0.85 5.0Dichloroethane NA 12388HU   20 ml NA NA (anhydrous)

The reaction in Example 8 is described in the scheme below:

Example 9: Synthesis of TBDMS Esuberaprost TMSE Ester Side ChainCarbonylimidazole (12)

To a solution of TBDMS esuberaprost TMSE ester (4) (20 mg, 0.0326 mmol)in dichloromethane (1.5 mL) was added carbonyldiimidazole (8 mg, 0.0489mmol). The reaction mixture was stirred at ambient temperature underargon. After 8 h the reaction was found to be 30% complete based on TLC(EtOAc/Hexanes 3:7). The reaction was charged with additionalcarbonyldiimidazole (32 mg, 0.1956 mmol) in four portion over 40 h. Thereaction mixture was quenched with water (1 ml) and the organic layerwas separated, washed with brine (1 mL), dried over sodium sulfate andevaporated in vacuo to obtain crude TBDMS esuberaprost TMSE estercarbonylimidazole (12) (32 mg) (Lot #RD-UT-1206-032). The crude productwas characterized by ¹H NMR.

TABLE 9 Material used in Example 9 Name MW Lot No. Amount mmol Eq. TBDMSEsuberaprost 613.00 RD-UT- 20 mg 0.0326 1.0 TMSE ester (4) 1199-079Carbonyldiimidazole 162.15 BCBR6489V 40 mg 0.2445 7.5 (CDI)Dichloromethane NA 53200 1.5 mL  NA NA (anhydrous)

The reaction in Example 9 is described in the scheme below:

Example 10: Synthesis of TBDMS Esuberaprost TMSE Ester Side ChainPiperidine Carbamate (13)

To a solution of TBDMS esuberaprost TMSE ester side chaincarbonylimidazole (12) (30 mg, 0.0424 mmol) in tetrahydrofuran (1 mL)was added piperidine (21 μL, 0.2122 mmol) and water (50 μL). Thismixture was stirred at ambient temperature under argon. After 24 h thereaction was found to be 90% complete based on TLC (EtOAc/Hexanes 3:7).The reaction was charged with additional piperidine (21 μL, 0.2122 mmol)and water (100 μL) then stirred for another 6 h. The reaction mixturewas evaporated in vacuo and the residue was partitioned between ethylacetate (1 mL) and water (1 mL). The organic layer was separated, washedwith brine (1 mL), dried over sodium sulfate and evaporated in vacuo toobtain crude product (13). This was purified by silica gel columnchromatography using ethyl acetate and hexanes (0 to 10%) to obtain pureTBDMS esuberaprost TMSE ester side chain piperidine carbamate (13) (19.4mg) in 82.1% yield (over two steps) (Lot #RD-UT-1206-040). This productwas characterized by ¹H NMR.

TABLE 10 Material used in Example 10 Name MW Lot No. Amount mmol Eq.TBDMS Esuberaprost 707.07 RD-UT- 30 mg 0.0424 1.0 TMSE ester 1206-032side chain carbonyl- imidazole (12) Piperidine 85.15 0295026 42 μL0.4244 10 Tetrahydrofuran NA SHBJ0753 1 mL NA NA Water NA Tap 150 μL NANA

The reaction in Example 10 is described in the scheme below:

Example 11: Synthesis of Esuberaprost Side Chain Piperidine Carbamate(14)

To a solution of TBDMS esuberaprost TMSE ester side chain piperidinecarbamate (13) (30 mg, 0.0262 mmol) in anhydrous tetrahydrofuran (1 mL)was added tetra-n-butylammonium fluoride solution (157 μL, 0.1574 mmol).This mixture was stirred at ambient temperature under argon. After 2 h,the reaction was found to be complete based on TLC (MeOH/DCM 1:9). Thereaction mixture was quenched with water (1 mL) and ethyl acetate (2 mL)was added. The organic layer was separated, and the aqueous layer wasextracted with ethyl acetate (2×2 mL). The combined organic layers werewashed with brine, dried over sodium sulfate and evaporated in vacuo toobtain esuberaprost side chain piperidine carbamate (14) (20.5 mg) (Lot#RD-UT-1206-049). This was characterized by spectral data (′H NMR, ¹³CNMR and MS).

TABLE 11 Material used in Example 11 Name MW Lot No. Amount mmol Eq.TBDMS Esuberaprost 724.14 RD-UT-  19 mg 0.0262 1.0 TMSE side 1206-032chain piperidine carbamate (13) Tetra butylammonium 261.46 SHBJ8226 157μL 0.1574 6.0 fluoride (1.0M Solution in THF) Tetrahydrofuran NASHBJ0753  1 mL NA NA (anhydrous)

The reaction in Example 11 is described in the scheme below:

Exemplary Esuberaprost prodrugs prepared using methods described aboveare shown in the Table 12 below.

Name R₁ R₂ R₃ Esuberaprost Side CO₂CH₃ H OH Chain Methyl CarbonateEsuberaprost H CO₂CH₃ OH Cyclopentyl Methyl Carbonate Esuberaprost SideCONHCH₃ H OH Chain Monomethyl Carbamate Esuberaprost H CONHCH₃ OHCyclopentyl Monomethyl Carbamate Esuberaprost Side CON(CH₃)₂ H OH ChainDimethyl Carbamate Esuberaprost H CON(CH₃)₂ OH Cyclopentyl DimethylCarbamate Esuberaprost Side Chain Piperidine Carbamate

H OH Esuberaprost Cyclopentyl Piperidine Carbamate H

OH Esuberaprost Side Chain Bipiperidine Carbamate

H OH Esuberaprost Cyclopentyl Bipiperidine Carbamate H

OH Esuberaprost Side (CH₂)₂OP(O)(OH)₂ H OH Chain Ethyl PhosphateEsuberaprost H (CH₂)₂OP(O)(OH)₂ OH Cyclopentyl Ethyl PhosphateEsuberaprost Side P(O)(OH)₂ H OH Chain Phosphate Esuberaprost HP(O)(OH)₂ OH Cyclopentyl Phosphate Esuberaprost Cyclic Carbonate R₁ andR₂ connected to carbonyl to make cyclic carbonate

OH Esuberaprost Cyclic Phosphate R₁ and R₂ connected to phophosrous tomake cyclic phosphate

OH Esuberaprost alkyl H H NHSO₂R’ or aryl sulfonamide R’ = methyl,ethyl, aryl, substituted aryl etc. Esuberaprost Carboxylic Acid Amidesof Amino Acids Esuberaprost H H Glycine Glycine Amide Esuberaprost H HAlanine Alanine Amide Esuberaprost H H Arginine Arginine AmideEsuberaprost H H Asparagine Asparagine Amide Esuberaprost H H Asparticacid Aspartic Acid Amide Esuberaprost H H Cysteine Cystein AmideEsuberaprost H H Glutamine Glutamine Amide Esuberaprost H H GlutamicGlutamic Amide acid Esuberaprost H H Histidine Histidine AmideEsuberaprost H H Isoleucine Isoleucine Amide Esuberaprost H H LeucineLeucine Amide Esuberaprost H H Lysine Lysine Amide Esuberaprost H HMethionine Methionine Amide Esuberaprost H H Phenylalanine PhenylalanineAmide Esuberaprost Serine H H Serine Amide Esuberaprost H H TryptophanTryptophane Amide Esuberaprost H H Threonine Threonine AmideEsuberaprost H H Tyrosine Tyrosine Amide Esuberaprost H H Valine ValineAmide Esuberaprost H H Citrulline Citrilline Amide Esuberaprost H HOrnithine Ornithine Amide Esuberaprost Side Chain Esters of Amino AcidsEsuberaprost Glycine H OH Glycine Ester Esuberaprost Alanine H OHAlanine Ester Esuberaprost Arginine H OH Arginine Ester EsuberaprostAsparagine H OH Asparagine Ester Esuberaprost Aspartic acid H OHAspartic Acid Ester Esuberaprost Cystein H OH Cystein Ester EsuberaprostGlutamine H OH Glutamine Ester Esuberaprost Glutamic acid H OH GlutamicEster Esuberaprost Histidine H OH Histidine Ester EsuberaprostIsoleucine H OH Isoleucine Ester Esuberaprost Leucine H OH Leucine EsterEsuberaprost Lysine H OH Lysine Ester Esuberaprost Methionine H OHMethionine Ester Esuberaprost Phenylalanine H OH Phenylalanine EsterEsuberaprost Serine Serine H OH Ester Esuberaprost Tryptophan H OHTryptophane Ester Esuberaprost Threonine H OH Threonine EsterEsuberaprost Tyrosine H OH Tyrosine Ester Esuberaprost Valine H OHValine Ester Esuberaprost Citrulline H OH Citrilline Ester EsuberaprostOrnithine H OH Ornithine Ester Esuberaprost Cyclopentyl Esters of AminoAcids Esuberaprost H Glycine OH Glycine Ester Esuberaprost H Alanine OHAlanine Ester Esuberaprost H Arginine OH Arginine Ester Esuberaprost HAsparagine OH Asparagine Ester Esuberaprost H Aspartic acid OH AsparticAcid Ester Esuberaprost H Cysteine OH Cystein Ester Esuberaprost HGlutamine OH Glutamine Ester Esuberaprost H Glutamic acid OH GlutamicEster Esuberaprost H Histidine OH Histidine Ester Esuberaprost HIsoleucine OH Isoleucine Ester Esuberaprost H Leucine OH Leucine EsterEsuberaprost H Lysine OH Lysine Ester Esuberaprost H Methionine OHMethionine Ester Esuberaprost H Phenylalanine OH Phenylalanine EsterEsuberaprost H Serine OH Serine Ester Esuberaprost H Tryptophan OHTryptophane Ester Esuberaprost H Threonine OH Threonine EsterEsuberaprost H Tyrosine OH Tyrosine Ester Esuberaprost H Valine OHValine Ester Esuberaprost H Citrulline OH Citrilline Ester EsuberaprostH Ornithine OH Ornithine Ester

In addition, where features or aspects of the disclosure are describedin terms of Markush groups, those skilled in the art will recognize thatthe disclosure is also thereby described in terms of any individualmember or subgroup of members of the Markush group.

As will be understood by one skilled in the art, for any and allpurposes, particularly in terms of providing a written description, allranges disclosed herein also encompass any and all possible subrangesand combinations of subranges thereof. Any listed range can be easilyrecognized as sufficiently describing and enabling the same range beingbroken down into at least equal halves, thirds, quarters, fifths,tenths, etc. As a non-limiting example, each range discussed herein canbe readily broken down into a lower third, middle third and upper third,etc.

As will also be understood by one skilled in the art all language suchas “up to,” “at least,” “greater than,” “less than,” and the like,include the number recited and refer to ranges which can be subsequentlybroken down into subranges as discussed above. Finally, as will beunderstood by one skilled in the art, a range includes each individualmember.

All publications, patent applications, issued patents, and otherdocuments referred to in this specification are herein incorporated byreference as if each individual publication, patent application, issuedpatent, or other document was specifically and individually indicated tobe incorporated by reference in its entirety. Definitions that arecontained in text incorporated by reference are excluded to the extentthat they contradict definitions in this disclosure.

Other embodiments are set forth in the following claims.

What is claimed is:
 1. A compound represented by Formula (I), or adiastereomer, enantiomer or pharmaceutically acceptable salt of thecompound:

wherein R¹ and R² each independently represent H, C₁-C₆ alkyl, —CO₂R⁶,—CONR⁶R⁷, —P(O)(OH)₂—, —(CH₂)₂OP(O)(OH)₂— or a hydroxy protecting group,or wherein OR¹ or OR² forms an ester of an amino acid, or wherein R¹ andR² are connected to carbonyl to make a cyclic carbonate group, orwherein OR¹ or OR² together form a phosphate group; R³ represents NR⁷R⁸,OR⁹, or NHSO₂R¹⁰; R⁴ represents H or C₁₋₃ alkyl; R⁵, R⁶ and R⁷ eachindependently represent H or C₁₋₆ alkyl, or wherein R⁶ and R⁷ togetherwith the nitrogen to which they are attached form a piperidine or abipiperidine ring; R⁸ represents H, optionally substituted C₁-C₆ alkyl,or

or wherein R⁷ and R⁸ are such that NR⁷R⁸ is an amide of an amino acid;R⁹ represents H or C₁-C₆ alkyl, which may be optionally substituted witha terminal hydroxyl or carboxy group; and R¹⁰ represents H, optionallysubstituted C₁-C₆ alkyl, optionally substituted C₆-C₁₀ aryl, optionallysubstituted C₃-C₈ heteroaryl or optionally substituted heterocyclyl;with a proviso that all of R² and R⁸ are not H.
 2. The compoundaccording to claim 1, wherein R¹ is selected from the group consistingof H, —CO₂CH₃, —CONHCH₃, —(CH₂)₂OP(O)(OH)₂, —P(O)(OH)₂—,

and an amino acid; wherein R² is H; and wherein R³ is OH.
 3. Thecompound according to claim 1, wherein R² is selected from the groupconsisting of H, —CO₂CH₃, —CONHCH₃, —(CH₂)₂OP(O)(OH)₂, —P(O)(OH)₂—,

and an amino acid; wherein R¹ is H; and wherein R³ is OH.
 4. Thecompound according to claim 1, wherein R¹ and R² are connected tocarbonyl to make a cyclic carbonate group.
 5. The compound according toclaim 1, wherein OR¹ or OR² together form a phosphate group.
 6. Thecompound according to claim 1, wherein R¹ and R² each represent H, R³represents NR⁷R⁸; wherein R₇ is H or optionally substituted C₁-C₆ alkyl;and R₈ is

R⁶ and R⁹ each independently represent H or C₁-C₆ alkyl.
 7. The compoundaccording to claim 1, wherein R¹ and R² each represent H, R³ representsNHSO₂R¹⁰; wherein R¹⁰ is selected from optionally substituted C₁-C₆alkyl or optionally substituted C₆-C₁₀ aryl group.
 8. The compoundaccording to claim 1, wherein the amino acid is selected from the groupconsisting of glycine, alanine, arginine, asparagine, aspartic acid,cysteine, glutamine, glutamic acid, histidine, isoleucine, leucine,lysine, methionine, phenylalanine, serine, tryptophan, threonine,tyrosine, valine, citrulline, or ornithine, and combinations thereof. 9.A compound selected from the group consisting of:


10. A process for the preparation of a compound of Formula (III):

comprising: (a) reacting a compound of Formula (II)

with methanesulfonic acid, optionally in the presence of at least onecarboxyl-activating agent, optionally in the presence of at least onesuitable coupling agent, to form a compound of Formula (II′)

(b) deprotecting the product of Formula (II′) of step (a) in acidiccondition to form the compound of Formula (III).
 11. The process ofclaim 10, wherein the carboxyl-activating agent is1,1′-carbonyldiimidazole, and the coupling agent is1,8-diazabicyclo[5.4.0]undec-7-ene.
 12. The process of claim 10, whereinthe deprotecting of step (b) uses HCl in methanol.
 13. A process for thepreparation of a compound of Formula (VI):

comprising: (b) reacting a compound of Formula (IV)

with 4-nitrophenyl chloroformate, optionally in the presence of excessof at least one amine base to form a compound of Formula (V);

(b) desilylating the compound of Formula (V) of step (a) to form thecompound of Formula (VI).
 14. The process of claim 13, wherein the aminebase comprises pyridine and dimethylamine.
 15. A process for thepreparation of a compound of Formula (VIII):

comprising: (a) reacting a compound of Formula (IV)

with methyl chloroformate, optionally in the presence of at least oneamine base to form a compound of Formula (VII);

(b) desilylating the compound of Formula (VII) of step (a) to form thecompound of Formula (VIII).
 16. The process of claim 15, wherein theamine base is N,N,N′,N′-tetramethylethylenediamine.
 17. The process ofclaims 13-16, wherein the desilylating of step (b) usestetrabutylammonium fluoride.
 18. A process for the preparation of acompound of Formula (XI):

comprising: (a) reacting a compound of Formula (IX)

with glycine methyl ester hydrochloride, optionally in the presence ofat least one carboxyl-activating agent, optionally in the presence of atleast one amine base to form a compound of Formula (X);

(b) hydrolyzing the ester of Formula (X) of step (a) to form thecompound of Formula (XI).
 19. The process of claim 18, wherein thecarboxyl-activating agent is1-ethyl-3-(3′-dimethylaminopropyl)carbodiimide hydrochloride, and theamine base is triethylamine.
 20. The process of claim 18, wherein thehydrolyzing of step (b) uses trimethyltin hydroxide.
 21. A process forthe preparation of a compound of Formula (XIV):

comprising: (a) reacting a compound of Formula (IV)

with carbonyldiimidazole to form a compound of Formula (XII);

(b) reacting a compound of Formula (XII) with piperidine to form acompound of Formula (XIII);

(c) desilylating the compound of Formula (XIII) of step (b) to form thecompound of Formula (XIV).
 22. The process of claim 21, wherein thedesilylating of step (b) uses tetrabutylammonium fluoride.
 23. Theprocess of any one of claims 10-22 conducted in the presence of one ormore solvents selected from the group consisting of tetrahydrofuran,methanol, dichloromethane, dichloroethane, and water.